Temperature stable compositions and processes for brightening metals and alloys

ABSTRACT

Metals and alloys are subjected to a microfinishing treatment with a chemical bright dip composition comprising an aqueous solution of nitric acid, hydrochloric acid, and a betaine derivative. Preferably, the solution also includes phosphoric acid and/or sulphuric acid, particularly when the surface to be treated is any of the various low-expansion nickel alloys, such as Kovar, Invar, Rodar or Therlo.

United States Patent Arciniega TEMPERATURE STABLE COMPOSITIONS AND PROCESSES FOR BRIGHTENING METALS AND ALLOYS Inventor: Rodolfo Arciniega, Dallas, Tex.

Texas Instruments Incorporated, Dallas, Tex.

Filed: Apr. 16, 1973 Appl. No: 351,718

Assignee:

US. Cl. 156/20, 252/794 Int. Cl C23g 1/00 Field of Search 156/20; 252/792, 79.4, 252/795 References Cited UNITED STATES PATENTS ll/l954 Hayes et al. 252/794 Oct. 1, 1974 3,072,5l5 l/l963 von Smolinski et al. 156/20 Primary Examiner-William A. Powell Assistant ExaminerBrian J. Leitten Attorney, Agent, or Firm-Harold Levine; James T. Comfort; Gary C. I-loneycutt 5 7 ABSTRACT 20 Claims, N0 Drawings TEMPERATURE STABLE COMPOSITIONS AND PROCESSES FOR BRIGHTENING METALS AND ALLOYS A preferred alloy used in the fabrication of headers for transistors and semiconductor circuits is composed primarily of iron, nickel and cobalt, designated ASTM F- alloy and generally known as Kovar. Such headers are usually etched and oxidized prior to subsequent use in glass sealing operations. They must be deoxidized and brightened prior to plating in order to restore the smooth surface that existed prior to etching and oxidation. Various chemical microfinishing solutions are commercially available for brightening Kovar, including particularly various mixtures of nitric, hydrochloric, and phosphoric acids. It is also known, as in U.S. Pat. No. 3,530,017, to add various surfactants to such acid solutions for modifying their chemical action so that a smooth finish is produced with a minimum dissolution or pitting of the metal surfaces.

Such prior surfactant-containing solutions have been found to have a limited storage life, particularly in hot weather, and have also been found to degrade rapidly in use at high temperatures, presumably due to the oxidation of the surfactant by the nitric acid contained in the solution. Accordingly, it is a primary object of the present invention to provide a chemical microfinishing solution having a prolonged storage life and which exhibits little or no significant thermal degradation during prolonged use at optimum working temperatures.

One aspect of the invention is embodied in a composition comprising 1 to percent by weight of hydrochloric acid, 1 to 10 percent by weight of nitric acid, 0.05 to 10 percent by weight of a betaine derivative, and the remainder water, The betaine derivative is selected from an alkyl betaine, an aralkyl betaine, an

alkyl ammonium sulfonic acid betaine, and an acyl amido ammonium sulfonic acid betaine. Preferably, the composition also includes 5 to 50 percent by weight of phosphoric acid, or 5 to 30 percent by weight sulphuric acid, or a combination of these percentages of phosphoric and sulphuric acids.

The method embodiments of the invention are carried out by contacting a metal or alloy surface with the improved composition as defined above for a period of time and at an elevated temperature sufficient to produce a 'microfinished surface with controlled removal of metal. Normally, a temperature of 130 to 200 F. is employed, and preferably a temperature of 160 to 190 F. The time required to achieve a suitable polishing will vary somewhat depending upon the composition and temperature of the bath, the type of metal surface to be microfinished and the condition of the surface. For normal microfinishing, the time required is ordinarily about 3 minutes up to about 30 minutes, and preferably about 5 to 10 minutes.

No special equipment is required for practicing the process of the invention. Readily available acidresistant containers and heating elements are the only equipment required.

The key ingredient of the new composition is the betaine derivative. Betaine-is a well-known alkaloid, also known as the anhydride of carboxymethyltrimethylammonium hydroxide-The alkyl and the aralkyl betaines of the invention are readily produced by reacting betaine with an aliphatic or araliphatic alcohol having 6 to 20 carbon atoms. For example, betaine is reacted with hexanol to produce hexylbetaine; with cetyl alcohol to produce cetyl betaine; with octadecyl alcohol to obtain octadecyl betaine; with lauryl alcohol to obtain lauryl betaine. The alkyl ammonium sulfonic acid betaines and the acyl amido ammonium sulfonic acid betaines'are commercially available, as are most of the alkyl betaines.

1 Optionally the microfinishing baths of the invention may also include one or more surfactants in addition to the alkyl or aralkyl betaine. The optional surfactant may be one of the compounds described in U.S. Pat.

No. 3,072,515. These surfactants are (l condensation products of 1 mole of phenol with about 5 moles of ethylene oxide, (2) condensation products of 1 mole of an alkyl phenol having up to about 15 carbon atoms in the alkyl group with about 5 30 moles of ethylene oxide, (3) condensation products of 1 mole of an alkyl amine having about 10 20 carbon atoms in the alkyl group with about 5 50 moles of ethylene oxide, (4) condensation products of 1 mole of an aliphatic alcohol having about 10 20 carbon atoms in the alkyl group with about 5 50 moles of ethylene oxide, (5) condensation products of 1 mole of a polypropylene glycol containing about 10 50 propylene oxide units with about 4 150 moles of ethylene oxide, and (6) mixtures thereof.

Alternatively, other optional surfactants can be employed which contain an aliphatic chain of 6 to 20 carbon atoms. A preferred group of surfactants includes the cationic aliphatic, araliphatic and heterocyclic amines, non-ionic and anionic aliphatic acid amides, non-ionic aliphatic acid partial esters of polyhdric alcohols and their polyoxyethylene ethers, anionic aliphatic sulfates, anionic aliphatic esters of sulfonated aliphatic acids, anionic aliphatic aryl polyether sulfonates, and anionic aliphatic phosphates.

The cationic aliphatic, araliphatic and heterocyclic amines are primary, secondary, tertiary and quaternary amines containing at least one aliphatic chain of 6 to 20 carbon atoms, which may be a straight or branched chain. Representative compounds include the mono-, diand tri-n-alkyl fatty amines. Exemplary compounds include the primary, secondary and tertiary fatty amines identified by the trade name Armeen.

Other compounds include the alkyl and the aralkyl quaternary ammonium 'salts. Preferred compounds of this type contain one alkyl group having from 8 to 16 carbon atoms, two alkyl groups having from 1 to 6 carbon atoms, and an aralkyl group having from 7 to 10 carbon atoms, such as alkyl dimethyl ethylbenzyl ammonium chloride identified by the trade name Onyx BTC 471.

The heterocyclic amines include the substituted glyoxalidines and the substituted oxazolines, employed as their acid addition salts. Representative compounds include l-hydroxyethyl-2-heptadecenyl glyoxalidine identified by the trade name Alro Amine 0, and a substituted oxazoline identified by the trade name Alkaterge C.

The non-ionic aliphatic acid amides include the amides of preferably lower aliphatic amines such as amino-ethyl ethanolamine and diethanolamine and fatty acids having a straight or branched aliphatic chain of 6 to carbon atoms. Representative compounds include aminoethyl ethanolamine fatty acid amides identified by the trade name Nopcogen RP and diethanolamine fatty acid amide identified by the trade name Ninol 1001.

The anionic aliphatic acid amides includes the amides of 6 20 carbon atom straight or branched chain aliphatic acids with preferably lower aliphatic aminosulfonic and aminocarboxylic acids. The amino group preferably is also substituted with a l 6 carbon atom alkyl group. Representative compounds include sodium N-cyclohexyl-N-palmitoyl-taurate identified by the trade name Igepon CN-42, sodium N-methyl-N- oleoyltaurate identified by the trade name Igepon T-33, and N-methyl-N-oleoylglycine identified by the trade name Sarkosyl 0.

The non-ionic aliphatic acid partial esters of polyhydric alcohols and their polyoxyethylene ethers include the 6 20 carbon atom straight or branched chain aliphatic acid partial esters of sorbitol, propylene glycol, and glycerol, and their polyoxyethylene ethers. Representative compounds are sorbitan monooleate identified by the trade name Span 80 and polyoxyethylene sorbitan monooleate, called Tween 80.

The anionic aliphatic sulfates includes the 6 20 carbon atom straight or branched chain alkyl sulfates or sulfate esters. A representative compound is sodium lauryl sulfate identified by the trade name Duponol C.

The anionic aliphatic esters and amides of sulfonated dicarboxylic acids include the 6 20 carbon atom straight or branched alkyl esters of sulfonated lower dicarboxylic acids. A representative compound is sodium sulfosuccinic acid dioctyl ester identified by the trade name Aerosol OT and disodium N-octadecylsulfosuccinamate identified by the trade name Aerosol 18.

The anionic aliphatic aryl polyether sulfonates include the 6 20 carbon atoms straight or branched chain alkyl substituted aryl polyether sulfonates. A representative compound is sodium octyl phenoxy polyethoxy sulfonate identified by the trade name Triton X-200. 1

The anionic aliphatic phosphates includes the 6 20 carbon atom straight or branched chain alkyl monoand polyphosphates containing up to 8 phosphate radicals. Representative compounds include (2-ethylhexyl) -Na (l O identified by the trade name Victawet 35B and (capryl) -Na (P O identified by the trade name Victawet 58B and monophosphates such as lauryl ester of ortho phosphoric acid.

Additional surfactants which may be employed include the anionic fluorinated aliphatic compounds such as Floro-chemical FC-95 and the amphoteric surfactants such as the ethoxylated sodium salt Triton QS-lS.

The following examples illustrate various microfinishing formulations of the invention. The acids are considered to be of 100 percent strength.

EXAMPLE l-Continued Nitric Acid 4% by weight Cetyl Bctaine 0.371 by weight Water Remainder EXAMPLE 2 Phosphoric Acid 147: by weight Sulfuric Acid 10% by weight Hydrochloric Acid 2% by weight Nitric Acid 371 by weight Cetyl Bctaine 0.25% by weight Triton X-l00 0.20% by weight Water Remainder EXAMPLE 3 Phosphoric Acid 27% by weight Hydrochloric Acid 3% by weight Nitric Acid 4% by weight Lauryl Bctaine 0.25% by weight Triton X-lOO 0.20% by weight Water Remainder EXAMPLE 4 Sulfuric Acid 307: by weight Hydrochloric Acid 3% by weight Nitric Acid 4% by weight Stearyl Betainc 0.25% by weight Triton X-lOO 0.20% by weight Water Remainder EXAMPLE 5 Hydrochloric Acid 6% by weight Nitric Acid 5% by weight Cetyl Betainc 1% by weight Triton X-l00 0.5% by weightv Water Remainder EXAMPLE 6 Hydrochloric Acid 6% by weight Nitric Acid 5% by weight Cetyl Bctaine 1.5% by weight Water Remainder Aralkyl betaines may be substituted for the alkyl betaines specified in the above Examples, including phenylheptyl betaine, xylylhexyl betaine and tolyloctyl betaine. Alkyl ammonium sulfonic acid betaines or acyl amido ammonium sulfonic acid betaines may also be substituted in each of the above Examples, including cetyl, lauryl, stearyl or oleoyl ammonium sulfonic acid betaines, and the corresponding acyl amido ammonium sulfonic acid betaines.

As noted above, hydrochloric and nitric acids are the essential, active acids of the composition. For best results, however, the phosphoric and/or sulfuric acids are frequently essential to ensure smooth chemical polishing without etching or pitting.

Similarly, the betaine derivative is a sufficient surfactant by itself for most applications; however, the addition of another surfactant from the optional list, preferably an alkyl aryl polyether alcohol, can be very useful to eliminate the smut formation that sometimes occurs without it. Alternatively, the smut can be removed by brief immersion in an alkaline permanganate solution at an elevated temperature, followed by a short dip in hydrochloric acid.

What is claimed is:

l. A composition comprising 1 20 percent by weight of hydrochloric acid, 1 percent by weight of nitric acid, 0.05 10 percent by weight of a betaine derivative selected from an alkyl ammonium sulfonic acid betaine, an acyl amido ammonium sulfonic acid betaine, and an alkyl or aralkyl betaine; and the remainder water.

2. A composition as in claim 1 further comprising 5 50 percent by weight of phosphoric acid.

3. A composition as in claim 1 further comprising 5 30 percent by weight sulfuric acid.

4. A composition as in claim 2 further comprising 5 30 percent by weight sulfuric acid.

5. A composition as in claim 1 further including 0.02 5 percent by weight of an alkyl aryl polyether alcohol.

6. A composition as in claim 2 further including 0.02 5 percent by weight of a lkyl aryl polyether alcohol.

7. A composition as in claim 3 further including 0.02 5 percent by weight of an alkyl aryl polyether alcohol.

8. A composition as in claim 4 further including 0.02 5 percent by weight of an alkyl aryl polyether alcohol.

9. A composition as in claim 1 wherein said betaine is cetyl betaine.

10. A composition as in claim 2 wherein said betaine is cetyl betaine.

11. A composition as in claim 3 wherein said betaine is cetyl betaine.

12. A composition as in claim 4 wherein said betaine is cetyl betaine.

13. A composition as in claim 5 wherein said betaine is cetyl betaine.

14. A composition as in claim 6 wherein said betaine is cetyl betaine.

15. A composition as in claim 7 wherein said betaine is cetyl betaine.

16. A composition as in claim 8 wherein said betaine is cetyl betaine.

claim4. 

1. A COMPOSITION COMPRISING 1-20 PERCENT BY WEIGHT OF HYDROCHLORIC ACID 1-10 PERCENT BY WEIGHT OF NITRIC ACID, 0.05 -10 PERCENT BY WEIGHT OF A BETAINE DERIVATIVE SELECTED FROM AN ALKYL AMMONIUM SULFONIC ACID BETAINE, AND AN ALKYL OR ARALKYL MONIUM SULFONIC ACID BETAINE, AND AN ALKYL OR ARALKYL BETAINE; AND THE REMAINDER WATER.
 2. A composition as in claim 1 further comprising 5 - 50 percent by weight of phosphoric acid.
 3. A composition as in claim 1 further comprising 5 - 30 percent by weight sulfuric acid.
 4. A composition as in claim 2 further comprising 5 - 30 percent by weight sulfuric acid.
 5. A composition as in claim 1 further including 0.02 - 5 percent by weight of an alkyl aryl polyether alcohol.
 6. A composition as in claim 2 further including 0.02 - 5 percent by weight of a lkyl aryl polyether alcohol.
 7. A composition as in claim 3 further including 0.02 - 5 percent by weight of an alkyl aryl polyether alcohol.
 8. A composition as in claim 4 further including 0.02 - 5 percent by weight of an alkyl aryl polyether alcohol.
 9. A composition as in claim 1 wherein said betaine is cetyl betaine.
 10. A composition as in claim 2 wherein said betaine is cetyl betaine.
 11. A composition as in claim 3 wherein said betaine is cetyl betaine.
 12. A composition as in claim 4 wherein said betaine is cetyl betaine.
 13. A composition as in claim 5 wherein said betaine is cetyl betaine.
 14. A composition as in claim 6 wherein said betaine is cetyl betaine.
 15. A composition as in claim 7 wherein said betaine is cetyl betaine.
 16. A composition as in claim 8 wherein said betaine is cetyl betaine.
 17. A method for treating a metal surface which comprises contacting the surface with a composition as in claim
 1. 18. A method for treating a metal surface which comprises contacting the surface with a coMposition as in claim
 2. 19. A method for treating a metal surface which comprises contacting the surface with a composition as in claim
 3. 20. A method for treating a metal surface which comprises contacting the surface with a composition as in claim
 4. 